COMPARISON OF μ-CALPAIN ACTIVITY IN SKELETAL MUSCLE OF BROILER AND LAYER

Abstract

It is well known that calpain [EC 3.4.22.l7] plays an important role in the
degradation of myofibrillar protein. The amount of mlpain present in atrophying
muscle tissue (where myofibril degradation is proceeding rapidly) is several-fold
greater than that isolated from normal muscle tissue. The muscle protein degradation rates of layers are higher than those of broiler chickens, and exhibited downward trends with aging of chickens. It is likely that differences among genetic stocks in muscle protein degradation rate are related to protease activity in muscle. The μ-calpain, has now been purified from a number of sources including rabbit, bovine chicken hamster and human skeletal muscle. A second calpain that requires only l to70 μ M Ca²⁺ for half-maximal activity (μ —calpain) has been purified from all the sesame tissues with the exception of human and chicken skeletal muscle. Recent data reported that chicken breast muscle has three calpain, two requiring retillimolar Ca²⁺ (μ-calpain and high μ-calpain) and one requiring rnicromolar Ca²⁺ (μ -calpain). The results showed that by using fluorescence assay, the calpain activities of broilers were lower than those of layers. μ-calpain activity in skeletal muscle was vary among the breeds that have difierent rates of muscle production.